Thank you for your answer!
Yes, you're right I could limit the connections with connection limit, I didn't think about it. But it still doesn't solve the problem. Correct me if I'm wrong, but connection limit includes also static requests - so I should set it to about 5-10 to let the browser download all static content as well. But still 5-10 dynamic requests per second (+ all regular from other IPs) may sometimes kill the website.
And if I understand dyn reqs throttling correctly, with 10 GET / requests, it should throttle it with my settings for 10 seconds (1 request / sec). However I noticed, that all of them are executed immediately (simultaneously). Is that correct?